Electromagnetic circuits and apparatus



May 6, 1930. w. FONDILLER ELECTROMAGNETIC CIRCUITS AND APPARATUS FiledDec. 17, 1926 kw W mm Wmfl WV. W W

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WILLIAM FONDIL LER, OF YO'NKERS, NEW YORK, -.ASSIGI\TOB TO WESTERNELECTBIC COMPANY, INCORPORATED, OF NEJV YORK, N. 2., ii. CORPORATIOTZKOF NERV YORK ELECTROMAGNETIC cmcura's Ann APPARATUS;

' Application filed December 17, 1926. Serial no. 155,513.

This invention relates to electromagnetic tion with the accompanyingdrawing in circuits and apparatus, particularly to their which:application in signaling systems. Fig. 1 is a diagrammatic illustrationof a An object of the invention is to secure concarrier wave telephonesystem containing 5 stancy of operating characteristics in elecmagneticelements in accordance with the intromagnetic circuits and apparatusemployvention; and 1 ing low field strengths. Fig. 2 is a magnetiaationcurve of a par- A related object of the invention is to re-. ticularcobalt steel alloy which may be cinduce distortion due to energydissipation'and ployed as the core material in the e1eDtr0- 19intermodulation in signaling systems. magnetic circuits of Fig. 1.

It is well known that when iron and most Fig. 1 shows the west terminalof a carmagnetic compositions ofiron are subjected rier wave telephonesystem connected to the to magnetic fields setup by signalingcurmultiplex transmission line ML. The usual rents, the permeability andhysteresis losses east terminal, which is similar to the west 5 varyappreciably with changes in the field terminal, is omitted for the sakeof simplistrength or in the resultant flux density. fying the showing. Asystem of this general Such variations in magnetic characteristics typeis illustrated in Fig. 42 of an article enproduce distortion in thesignaling currents, titled Carrier current telephony and telegwhich isvariously characterized as modularaphy by- Messrs. Colpitts andBlackwell,

tion, flutter efi'ect, etc., depending upon the published in theTransactions of the Americonditions under which it is produced. canInstitute of Electrical Engineers, vol.

The present invention relates particularly 40, 19?1. to magneticcircuits containing cobalt steel The terminal apparatus includes aplural-' alloys which exhibit relative constancy of ity of transmittingand receiving channels of 25 magnetic characteristics over a range ofwhich the transmitting channel TC and the magnetizing forcesincludingthe forces ordireceiving channel RC are typical. The channarilyemployed in signaling. These componel TO includes a modulator M, anoscillator sitions have heretofore been used extensively and .a' bandfilter F, and the channel RC for permanent magnets because of their highincludes a demodulator amplifier DA and a 30 coercivity at largemagnetizing forces, but band filter F. These channels are connected soaccording to the present invention are used to a low frequency telephoneline L by means in circuits employing low magnetizing forces, of aspecial balanced transformer H and bal-- in which region these alloyshave been found 'ancing network N. The band filters F and to exhibit lowCoercivity with accompanying F are ofthe well known type disclosed in 5constant permeability and low hysteresis U. S. Patent No. 1,227,113 toG. A. Campbell,

loss. issued May 22, 1917, and comprise a plural- The characteristics ofsubstantially conity of inductance coils and condensers arstantpermeability and low hysteresis los's exranged to pass with negligibleattenuation hibited by these alloys in the range of magwaves comprisedwithin predetermined bands as netizing forces below five gauss renderthem of frequencies, and substantially to suppress especiallyserviceable as the core material for Waves of all other frequencies. Themultitransformers, loading coils, filter inductance plex transmissionline ML is loaded at suitcoils, sensitive electrical measuringinstruable intervalsby means of loading coils C, ments, etc., whereuniformity of character-. only one of which is shown in the drawing.

45 istics over the operating range is demanded. Carrier waves areqtilized for transmission The advantage of obtaining a constant inoverthe line ML, a separate band of frequenductance with resulting lowenergy dissipacies being allotted to each channel. Voice tion and wavedistortion is obvious'to those frequency waves originating in the lowfreskilled in the art. quency line L pass through the balanced 50 Theinvention will be described in connec transformer H into the modulator Mwhere the oscillator 0. Of the components of modulation appearing in theoutput circuit of the modulator, the band filter Fmay suppress all butone sideband and the carrier, which it passes tothe multiplex line ML.In receiv-' ing 'signals,'the incoming carrier and sideband wavesassigned to the channel BC are selectively passed by the band filter Fand demodulated and amplified'in the demodulator-amplifier DA. The voicefrequency com ponents of demodulation appearing in the outputcircuit ofthe demodulator-amplifier DA are transmitted through balanced trans.

former coil H to the low frequency line L.

The apparatus which may employ the magnetic cobalt steel alloys as thecore material, according to the invention, are the balanced transfomerH, the inductance coils of the filters F and F and the loading coil C.Heretofore, it has been necessary in some cases to construct suchapparatus with air coresbecause of thehysteresis loss and the variationsin permeability attendant upon the use ofiron and other commonly usedmagnetic materials. Variations in these magnetic characteristics due toslight change in magnetizing force produce serious distortion in thesignalingv waves which greatly impairs the transmission efliciency ofthe system. According to this invention, stability of magneticcharacteristics is obtained by employing a hard'magnetic steel alloycontaining carbon, iron, cobalt and other elements as the'core materialin the electromagnetic field. Alloys suitable for this purpose have beenupon the market un-- der the trade name of KS steel.

The magnetization curve of Fig. 2 illus trates the relation between themagnetizing force H and the induced flux indensityB in c. g. s. units,for an alloy containing 35% cobalt, 7% tungsten, 2% chromium,.7%.carlion and the remainder iron. This relation is linear over therange of magnetizing forces from zero to about 5 gauss, the permeabilitybeing approximately 10.9 over this range. Tests on anotherrepresentative sample of this material were confined to the range ofmagnetizing forces from 0.025% gauss to 0.10 gauss, which includes therange of magnetizing forces ordinarily employed in signaling, thissample having a permeability of about 21 over this range. This lattersample was previously given a supplementary heat treatment whichaccounts for its higher permeability. The coercivity and hysteresis lossin each case are low. Other suitable cobalt-steel alloys are disclosedin U. S. Patents Nos. 1,338,132 and 1338,1133 to K. Honda, issued April27, 1920. By employing these magnetic materials for they magnetic coresin the magnetic circuits of Flg. 1 the transmission eiiiciency of thesystem is greatly improved.

alloys exhibiting similar pron scribed but included within the scope ofthe appended claims. For example other steel es may be employed in placeof cobalt steel, the term steell used in the claims referring to analloy of iron in which carbon is an essential element.

The invention claimed is:

1. The cpmbinatien with a magnetic material comprising a steel alloyconsisting chiefly of iron and cobalt having substantially constantpermeability at low magnetizing forces, of a magnetic circuit containingsaid material, and means for impressing upon said 7 circuit a pluralityof small magnetizing force components corresponding respectively tocomponents of a composite signaling wave.

2 The combination with a magnetic material comprisinga cobaltsteel alloycontaining from 5% to 60% cobalt and the balance chiefly iron, havingsubstantially constant per meability at low magnetizing forces, of amagnetic circuit containing said material,

and means for impressing upon said circuit a plurality of smallmagnetlzing force components corresponding respectively to components ofa composite signaling wave. 3. The combinatlon with a magnetic materialcomprising a steel alloy consistlng chiefly of iron and cobalt havingsubstantially constant permeability over a range of lowmagnetizing'forces, of a magnetic circuit con taining said material. andmeans for impressing upon said circuit a plurality of small magnetizingforce componentsnot exceeding the value at which the permeability of themagnetic material begins to vary substantially.

' 4. A signaling'system comprising an inductance the field of whichcontains a mag netic steel alloy consisting chiefly of iron and cobalthaving substantially constant permeability over a range of lowmagnetizing forces, and a circuit for impressing upon said inductance aplurality of small magnetizing force components comprised within saidrange. i 5. vA signaling for transmitting waves of differentfrequencies, and a filter for selectively passing certain of said waves,said filter comprising an inductance the field of which contains amagnetic steel alloy consisting chiefly of iron and cobalt and havingsubstantially constant persystem, comprising a circuit meability atmagnetizing forces ofthe order impressed upon said circuit.

6. A signaling system comprising a circuit for transmitting Waves ofdifferent frequencies, and a filter for selectively passing certain ofsaid waves, said filter comprising, an inductance the field of whichincludes a cobalt steel alloy containing from 5% to cobalt and thebalance chiefly iron and having substantially constant permeability atmagnetizing forces from zero to approximately five gauss.

In Witness whereof, I hereunto subscribe my name this 17th day ofDecember, A. D.

WILLIAM FONDILLER.

